Papers by Keyword: Velocity Profile

Abstract: 3D computational analyses are achieved to predict seriously the influences of thermal buoyancy strength and Dean number on Dean vortices, flow behavior and the rate heat transfer through 180° curved channel of square cross-sectional form. The work shows many results, so this paper emphasizes only on the results of 60° cross-sectional position of the bend duct. The principal partial equations of continuity, momentum and energy are considering in three dimensions under the following assumptions: flow is incompressible and laminar, and it is solved in steady-state. The aforementioned equations are subjected to suitable boundary conditions under following range as: Dean number of De = 125 to 150, Richardson number of Ri = 0 to 2 at fixed value of Prandtl number Pr = 1. The principal results of this work are illustrated as streamline and isotherm contours to draw to flow patterns and temperature distributions respectively. The axial velocity profile is shown versus above conditions, the local Nusselt number is also presented along the wall of 60° cross-sectional position. The results show that the thermal buoyancy can balance the effect of centrifugal force of fluid particles at the angular position of 60°.

Abstract: Transportation of fluids in pipelines is common in many industrial processes. The energy requirements for this transport is high because of the need to overcome the occurring frictional pressure drop or drag. However, the addition of high molecular weight polymers to fluid flows has been known to cause a reduction in the frictional pressure drop. It has also been reported to cause other changes in the flow including changes in the turbulence characteristics, holdup as well as asymmetry of the velocity profiles. In this work some experimental results are presented in order to gain better insight into the deviations from axisymmetry of velocity profiles of water flow in pipes when drag reducing agents are added. Drag reduction studies were carried out in a horizontal 14mmID acrylic pipe with hydrolyzed polyacrylamide and different molecular weights polyethylene oxide used as additives in fully developed flows. Asymmetry was observed at both transitional and turbulent flow regimes for all tested polymer types and it increased with molecular weights. While the molecular weight and degree of formation of entanglements and aggregates of the polymer fibers are indicated as the causes of the observed profile asymmetry, the contribution of system/setup imperfections can be ruled out.

Abstract: Turbulent fluid flow inside the vertical gasifier shaft having the porous insert has been numerically analyzed. The effect of the porous medium structure on the fluid flow has been studied. The mathematical model has been formulated in dimensional primitive variables using the realizable k-ε turbulent model. The distributions of velocity and skin friction coefficient inside the gasifier shaft have been obtained. The results clearly show an essential effect of the porous medium structure on turbulent fluid flow.

Abstract: The article investigates the counter-vortex flow, one of the most complex spatial nonuniform liquid and gas flows. Counter-vortex phenomenon implies an interaction of two or more wake coaxial circular-longitudinal lines twisted in opposite directions. The relevance of the research issue has determined the desirability of further research and application of unique hydraulic devices in the new situation based on the effect of the interaction of coaxial oppositely swirling flows of water in a circular pipe.

Abstract: An electrified liquid sheet injected into a dielectric moving through a viscous gas bounded by two horizontal parallel flat plates of a transverse electric field is investigated with the linear analysis method. The liquid sheet velocity profile and the gas boundary layer thickness are taken into account. The relationship between temporal growth rate and the wave number was obtained using linear stability analysis and solved using the Chebyshev spectral collocation method. The effects of the velocity profile on the stability of the electrified liquid sheet were revealed for both sinuous mode and varicose mode. The results show that the growth rate of the electrified Newtonian liquid is greater than that of corresponding Newtonian one under the same condition, and the growth rate of the sinuous mode is greater than that of the varicose mode. Keywords: instability; planar liquid sheet; velocity profile;spectral method;linear analysis

Abstract: Transverse and longitudinal velocity profiles on the xoy plane at z=0 and 5cm of side discharge jet under the action of crossflow and wave, velocity vectors on the xoy plane at z=0 and 5cm of side discharge jet under the action of wave and crossflow were measured by Micro ADV in this paper, respectively. Effects of wave and crossflow on velocity profiles and velocity vectors of side discharge jet were analyzed. The preliminary experimental results showed that transverse velocity profiles of side discharge jet centerline was less affected by crossflow and wave, however, effects on transverse and longitudinal velocities over the jet centerline were significant. Also, velocity vectors over of side discharge jet centerline were remarkably affected by wave and crossflow though velocity vectors on the jet centerline was less affected.

Abstract: Recently, microfluidics system has been widely employed in various areas for instance biomedical,pharmaceuticals and cell biological researchdue to its advantages. The flow behavior in microchannels with different cross-sections has been topic in previous studies. In this paper, numerical simulation of fluid flow in Forward Facing Step (FFS) configuration was performed to investigate velocity profile after the step. Reynolds numbers (Re) 100 with different step heights, 1μm and 3μm were used to observe trend occurs in the flow characteristics. The result illustrated an increase of velocity distribution with the increase of the step height.

Abstract: Keywords: river flow; two-dimensional CFD model; velocity profile; submerged vegetation leave Abstract. River flow with submerged foliage vegetation in straight and rectangular cross-sectional channel is numerically simulated through a vertical two-dimensional CFD model. Tilt thin strips are assigned in river flow to mimic the configuration of vegetation leave. The free surface line and the vertical profiles of longitudinal velocity are presented. The vertical velocity profile differs from the well acknowledged logarithmic or semi-logarithmic law. The submerged leave canopy resist the flow through it and pilots the flow upward over it, resulting in a decreased velocity within the canopy and an increased velocity above the canopy. The velocity profiles within the leave canopy are impacted by the configurations of the leave.

Abstract: In this paper, a state feedback control algorithm for non-holonomic robot to track a moving object is described. In order to generate continuous velocity profile, some independent time varying functions are introduced for calculation the state feedback variables. The simulation of the control algorithm is implemented with MATLAB. The results shows that, with the designed state feedback control algorithm, the wheeled mobile robot can track a moving object and the trajectory is also reasonable.

Abstract: No 460 oil-film bearing oil as the dedicated lubricant is regarded as the incompressible Newtonian fluid. To comprehensively analyze the real oil flow state, the mathematical model on velocity profiles, together with its dimensionless equations, is established, and the calculating program is developed to simulate the 3D velocity profiles and velocity gradients at different oil flow layers. The relationship between velocity profiles and the oil film pressure is discussed, and the velocity tendency is consistent with the general velocity profile of wedge cross section. The conclusions are beneficial to the further study on lubricating performances of heavy contact components and to prolong their service lives.